Longest Non-palindromic substring
Given a string of size n. The task is to find the length of the largest substring which is not a palindrome.
Examples:
Input : abba Output : 3 Here maximum length non-palindromic substring is 'abb' which is of length '3'. There could be other non-palindromic sub-strings also of length three like 'bba' in this case. Input : a Output : 0
A simple solution is to consider every substring and check if it is palindrome or not. Finally, return the length of the longest non-palindromic substring.
An efficient solution is based on the below approach.
Check for the case where all characters of
the string are same or not.
If yes, then answer will be '0'.
Else check whether the given string of size
'n' is palindrome or not.
If yes, then answer will be 'n-1'
Else answer will be 'n'
Implementation:
C++
// C++ implementation to find maximum length// substring which is not palindrome#include <bits/stdc++.h>using namespace std;// utility function to check whether// a string is palindrome or notbool isPalindrome(string str){ // Check for palindrome. int n = str.size(); for (int i=0; i < n/2; i++) if (str.at(i) != str.at(n-i-1)) return false; // palindrome string return true;}// function to find maximum length// substring which is not palindromeint maxLengthNonPalinSubstring(string str){ int n = str.size(); char ch = str.at(0); // to check whether all characters // of the string are same or not int i = 1; for (i=1; i<n; i++) if (str.at(i) != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n;}// Driver program to test aboveint main(){ string str = "abba"; cout << "Maximum length = " << maxLengthNonPalinSubstring(str); return 0;} |
Java
//Java implementation to find maximum length//substring which is not palindromepublic class GFG{ // utility function to check whether // a string is palindrome or not static Boolean isPalindrome(String str) { int n = str.length(); // Check for palindrome. for (int i = 0; i < n/2; i++) if (str.charAt(i) != str.charAt(n-i-1)) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome static int maxLengthNonPalinSubstring(String str) { int n = str.length(); char ch = str.charAt(0); // to check whether all characters // of the string are same or not int i = 1; for (i = 1; i < n; i++) if(str.charAt(i) != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver Program to test above function public static void main(String args[]) { String str = "abba"; System.out.println("Maximum Length = " + maxLengthNonPalinSubstring(str)); }}// This code is contributed by Sumit Ghosh |
Python 3
# Python 3 implementation to find maximum # length substring which is not palindrome# utility function to check whether# a string is palindrome or notdef isPalindrome(str): # Check for palindrome. n = len(str) for i in range(n // 2): if (str[i] != str[n - i - 1]): return False # palindrome string return True# function to find maximum length# substring which is not palindromedef maxLengthNonPalinSubstring(str): n = len(str) ch = str[0] # to check whether all characters # of the string are same or not i = 1 for i in range(1, n): if (str[i] != ch): break # All characters are same, we can't # make a non-palindromic string. if (i == n): return 0 # If string is palindrome, we can make # it non-palindrome by removing any # corner character if (isPalindrome(str)): return n - 1 # Complete string is not a palindrome. return n# Driver Codeif __name__ == "__main__": str = "abba" print("Maximum length =", maxLengthNonPalinSubstring(str))# This code is contributed by ita_c |
C#
// C# implementation to find maximum length// substring which is not palindromeusing System;class GFG { // utility function to check whether // a string is palindrome or not static bool isPalindrome(String str) { int n = str.Length; // Check for palindrome. for (int i = 0; i < n / 2; i++) if (str[i] != str[n - i - 1]) return false; // palindrome string return true; } // function to find maximum length // substring which is not palindrome static int maxLengthNonPalinSubstring(String str) { int n = str.Length; char ch = str[0]; // to check whether all characters // of the string are same or not int i = 1; for (i = 1; i < n; i++) if(str[i] != ch) break; // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can // make it non-palindrome by removing // any corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver code public static void Main() { String str = "abba"; Console.Write("Maximum Length = " + maxLengthNonPalinSubstring(str)); }}// This code is contributed by nitin mittal |
PHP
<?php// PHP implementation to find maximum length// substring which is not palindrome// utility function to check whether// a string is palindrome or notfunction isPalindrome($str){ $n = strlen($str); // Check for palindrome. for ($i = 0; $i < $n / 2; $i++) if ($str[$i] != $str[$n - $i - 1]) return false; // palindrome string return true;}// function to find maximum length// substring which is not palindromefunction maxLengthNonPalinSubstring($str){ $n = strlen($str); $ch = $str[0]; // to check whether all characters // of the string are same or not $i = 1; for ($i = 1; $i < $n; $i++) if($str[$i] != $ch) break; // All characters are same, we can't // make a non-palindromic string. if ($i == $n) return 0; // If string is palindrome, we can // make it non-palindrome by removing // any corner character if (isPalindrome($str)) return ($n - 1); // Complete string is not a palindrome. return $n;}// Driver code$str = "abba";echo "Maximum Length = ", maxLengthNonPalinSubstring($str);// This code is contributed by ajit?> |
Javascript
<script>//Javascript implementation to find maximum length //substring which is not palindrome // utility function to check whether // a string is palindrome or not function isPalindrome(str) { let n=str.length; // Check for palindrome. for (let i = 0; i < n/2; i++) { if(str[i] != str[n-i-1]) return false; } // palindrome string return true; } // function to find maximum length // substring which is not palindrome function maxLengthNonPalinSubstring(str) { let n = str.length; let ch=str[0]; // to check whether all characters // of the string are same or not let i = 1; for (i = 1; i < n; i++) { if(str[i] != ch) { break; } } // All characters are same, we can't // make a non-palindromic string. if (i == n) return 0; // If string is palindrome, we can make // it non-palindrome by removing any // corner character if (isPalindrome(str)) return n-1; // Complete string is not a palindrome. return n; } // Driver Program to test above function let str = "abba"; document.write("Maximum Length = " + maxLengthNonPalinSubstring(str)); // This code is contributed by avanitrachhadiya2155 </script> |
Output
Maximum length = 3
Time Complexity: O(n)
Auxiliary Space: O(n)
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